Co-encapsulation of enzyme and sensitive dye as a tool for fabrication of microcapsule based sensor for urea measuring

Enzyme based micron sized sensing system with optical readout was fabricated by co-encapsulation of urease and dextran couple with pH sensitive dye SNARF-1 into polyelectrolyte multilayer capsules. Co-precipitation of calcium carbonate, urease and dextran followed up by multilayer film coating and Ca-extracting by EDTA resulted in the formation of 3.5-4 micron capsules, what enable the calibrated fluorescence response to urea in concentration range from 10(-6) to 10(-1) M. The presence of urea can be monitored on a single capsule level as illustrated by confocal fluorescent microscopy. Variations in urease:dye ratio in capsules, applicability and limits of use of that type multi-component microencapsulated sensors are discussed.     

The evolution of the optical spectra of LaMnO<Subscript>3</Subscript> under light <Emphasis Type="Italic">n</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-type doping and the separation of phases

The optical absorption spectra of LaMnO₃ single crystals, pure and slightly doped with Ce and Sr (7%), were studied in the middle IR region. Ellipsometry measurements were performed in the visible region to determine real and imaginary permittivity parts. The energies of the onset of indirect transitions in LaMnO₃ at 293 and 80 K were found to be 0.30 and 0.40 eV, respectively. Impurity absorption bands corresponding to transition in hole and electron clusters were observed. The anomalous temperature dependence of IR absorption was explained by the existence of conducting droplets in the insulated doped crystal matrices at temperatures below the temperature of the appearance of a ferromagnetic contribution. The existence of such a contribution was proved by studying the equatorial Kerr effect. Because of the separation of phases, manganites slightly doped by a nonisovalent admixture can be treated as optically nonuniform media whose properties are similar to those of a composite system with metallic inclusions.     

Anomalies in the optical properties of nanocrystalline copper oxides CuO and Cu2O near the fundamental absorption edge

A 0.1–0.15-eV displacement of the fundamental absorption edge in the optical absorption spectra of nanocrystalline oxide n-CuO (relative to the position of the fundamental absorption edge in the spectra of CuO single crystals) towards lower energies (red shift) is observed against the background of strong blurring. Nanocrystalline n-Cu₂O exhibits a displacement of the fundamental absorption edge towards higher energies (blue shift) by approximately 0.35 eV. The size of crystallites in n-CuO and n-Cu₂O ranges from 10 to 90 nm. The blue shift of the fundamental absorption edge of n-Cu₂O is typical of classical wide-gap semiconductors and can be explained by size quantization upon a change in the particle size. The anomalous red shift of the fundamental absorption edge of the strongly correlated nanocrystalline oxide n-CuO can be attributed to the highly defective structure of n-CuO, anomalies in the electronic structure of strongly correlated compounds based on 3d metals, and their tendency to electronic phase separation with the formation of metal-like inclusions.     

Interference bandwidth compression of the spectrum of transition radiation from a modulated electron flux

The possibility of converting the modulated electron flux energy to electromagnetic oscillations (transition radiation) when the flux collides with an unmoved metallic screen is considered. The interference of waves arising at different sites of the screen changes the spectral-angular distribution of the radiation energy density. These changes are analyzed with allowance for a time delay between radiations coming from different parts of the inclined bunch. A plausible mechanism behind the frequency shift of interference maxima, which is observed when the angle of inclination of the screen is changed, is discussed.     

Gap solitons in an anharmonic diatomic lattice

Localized stationary modes with frequency in the forbidden region of the elastic vibrations of a diatomic anharmonic lattice are studied by the coupled-wave method. The mechanisms responsible for the brightening of the lattice in the cases of narrow and wide forbidden frequency bands are determined and an analytical expression is found for the stationary gap solitons. Fiz. Tverd. Tela (St. Petersburg) 39, 158–162 (January 1997)     

Preparation of polyelectrolyte microcapsules with silver and gold nanoparticles in a shell and the remote destruction of microcapsules under laser irradiation

A number of methods are proposed for encapsulating silver and gold nanoparticles into shells of polyelectrolyte microcapsules for the purpose of increasing the sensitivity of microcapsules to laser radiation. It is shown that capsules with nanocomposite shells can be remotely damaged under laser radiation with different powers and wavelengths. The sensitivity of capsules with silver and gold nanoparticles in shells to this radiation can be controlled by varying the conditions used for the preparation of the capsules. The release of the encapsulated material under laser radiation makes these systems promising for use as microcontainers intended for the target delivery of drugs in an organism.     

PHOTOHEMOLYSIS SENSITIZED BY PSORALEN: RECIPROCITY LAW IS NOT FULFILLED

The effect of the intensity of ultraviolet-A (UV-A) radiation (366 nm) on delayed photohemolysis sensitized by psoralen (PUV-A hemolysis) was studied. It was shown that PUV-A hemolysis induced by UV-A radiation at low fluence rate (20 W m-2) develops according to the well-known colloid-osmotic mechanism: there was no threshold dose of PUV-A treatment. After irradiation all the cells were hemolysed. The rate of PUV-A hemolysis was proportional to the square of the fluence. Hemolysis was delayed in the presence of sucrose. When the fluence rate of UV-A radiation was increased to 150 W m-2, the character of PUV-A hemolysis changed drastically. A threshold fluence appeared, below which PUV-A hemolysis was not induced. At fluences slightly exceeding the threshold, only part of the cells in the suspension were lysed. The dependence of the portion of hemolysing cells on fluence was S-shaped. Increasing the fluence resulted in complete (100%) hemolysis. The rate of complete hemolysis decreased at higher fluences, but was many-fold higher than the rate of low-intensity PUV-A hemolysis at equal fluences. The main features of high intensity PUV-A hemolysis (dependences on fluence and temperature, effect of sucrose) were the same for the hemolysis induced by the addition of previously photooxidized psoralen. We suggest that high intensity PUV-A hemolysis is induced with participation of photooxidized psoralen as an intermediate.     

Conformations of certain dialkylarylphosphines and their oxides

Conclusions It is characteristic of the conformations of the dialkylphenylphosphines and their oxides that the bisector of the CPC angle lies in the plane of the benzoyl ring. A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Branch of the Academy of Sciences of the USSR. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2243–2246, October, 1976.